Various load measuring devices and scales are known in the art. For example, U.S. Pat. No. 3,650,340 to Richard S. Bradley discloses a bending-beam structured load cell that is resistant to torque, moment, and end-forces, all of which affect the accuracy of the load cell. Most of the currently available scales generally depend on the stability of the loaded structure between the load cells for output stability and reduction of horizontal forces. For example, scales made by Weigh-Tronix utilizing multiple load cells provide chain links to reduce horizontal forces between load cells and absorb the energy from horizontal movement of the load on the scale. Other scales provide vertical cables to reduce diverse forces such as horizontal forces, thereby providing a substantially collimated force in the direction of force measurement. “Diverse forces” are herein used to refer to forces that are not in the direction of force measurement, while “collimated forces” are in the direction of force measurement. In the context of weight measurement, a vertical force would be a collimated force and horizontal forces would be diverse forces.
These scales, while reducing the adverse effect on measurement accuracy that is caused by horizontal forces, are expensive. The high cost associated with these scales are at least partly due to the massive support structures that are needed to suspend the flexible tension elements located between the load bearing structures and the load cells to reduce diverse forces horizontal forces between the load cells.
Although scales exist that do not require these massive and expensive support structures, these scales have other problems. Some scales include flexible compressive elements between the load cells and the load bearing structures. For example, scales made by Mettler Toledo and Cardinal provide rocker pins that are load cells with spherical ends and spherical or flat cups to reduce the horizontal forces. However, these scales are problematic in that they do not dampen the vibration or absorb energy adequately to prevent undesirable effects to the scale and on the force measurement when the scale is disturbed by the load. Although they can be made to dampen vibration and absorb adequate energy, doing so requires equipping these scales with an expensive check-rod system.
Some load cell manufacturers thread leveling feet into load cells with rubber pads to reduce the horizontal forces between the load cells that are coupled through the floor of the scale. These load cells must have large pads to support heavy loads because of the low load bearing strength of rubber pads. Rubber pads require level surfaces, vertically aligned feet, and rigid support structures. Otherwise, twisting and bending of the load cells due to diverse forces create errors in the load cell outputs.
Some other load cells get around this strict requirement for level surfaces by using leveling feet that are connected to the load cells with pivot joints. This arrangement allows uneven floors and misalignment but only reduces the forces caused by bending of the support structure.
What is needed is a durable load-transfer device that rapidly stabilizes and isolates r collimates vertical force in a cost-effective manner.